<p>The brown planthoppers (BPHs) are serious pests of rice in Southeast Asia which often cause a heavy loss of rice. Monitoring BPH populations and prediction of their damages to rice are more important for the precious control of this pest. Nowadays, highly efficient monitoring and predicting methods for BPHs are still rare. Here, the canopy temperatures of rice damaged by different number of BPHs were examined using the thermal imaging technique, and relationships between canopy temperature and population size of BPHs or rice yield were analyzed. The result showed that there was a significant and stable correlation between rice canopy temperatures and BPH population sizes on these rice plants in four consecutive years of plot experiments. Further, canopy temperatures of rice measured at 8:00–10:00 am were negatively related to the population size of BPHs, but not the temperature measured at noon and in the afternoon. Canopy temperatures of rice at booting and heading growth periods were also strongly related to the rice yield and its loss rate damaged by BPHs. Based on the difference between air temperature and mean canopy temperature of rice, the BPH population size could be monitored using an exponential function model, and the rice yield could be predicted by a linear model. A promising framework of automatic monitoring BPH populations was developed based on canopy temperatures of rice.</p>